document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=153189>Question 153189</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Hello,\r<BR>\n" );
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document.write( "How would I solve the following:\r<BR>\n" );
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document.write( "The level of thorium in a sample decreases by a factor of one-half every 4.2 million years.  A meteorite is discovered to have only 7.6% of its original thorium remaining.  How old is the meteorite?\r<BR>\n" );
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document.write( "I think this has been answered but I can not find the answer.\r<BR>\n" );
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document.write( "Please help me I have tried several time to solve this without any help but I just can seen to solve it.\r<BR>\n" );
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document.write( "Thank you,\r<BR>\n" );
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document.write( "Jimmy </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #112718 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=112718\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The level of thorium in a sample decreases by a factor of one-half every 4.2 million years. A meteorite is discovered to have only 7.6% of its original thorium remaining. How old is the meteorite? <BR>\n" );
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document.write( "A(t) = Ao(1/2)^(t/4.2 mil)<BR>\n" );
document.write( "This says \"the amount at time t A(t) is the amount you start with (Ao)<BR>\n" );
document.write( "multiplied by (1/2) (t/4.2 mil) times.<BR>\n" );
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document.write( "0.076Ao = Ao*(1/2)^(t/4.2 mil)<BR>\n" );
document.write( "0.076 = (1/2)^(t/4.2 mil)<BR>\n" );
document.write( "Take the log of both sides to get:<BR>\n" );
document.write( "log 0.076 = (t/4.2 mil)*log(1/2)<BR>\n" );
document.write( "t/4.2 mil = log0.076/log0.5<BR>\n" );
document.write( "t = 4.2 mil * 3.717857...<BR>\n" );
document.write( "t = 15.614998.. million years old.<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
document.write( " </SPAN>\n" );
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